How does a Direct Drive Variable Pitch Multicopter Achieve Yaw?

ASs stated, there seem to be several Direct Drive (Single Motor driving all props through gears/belts) Variable Pitch Multicopters, but i am confused as to how these obtain yaw motion.
I know that on independent drive multicopters, each motor can spin at a slightly different speed to achieve the desired yaw, but a multicopter with a single motor cannot achieve this through the same method.
Not sure how variable pitch could achieve a yawing motion either on a direct drive.

The easiest way I have found is to use a V-Tail although I am not using it right now for variable pitch. Otherwise, it would require a sensor to detect when the pitch is positive or negative then adjust the motors' speed accordingly or on a tricopter, reverse the rotation angle..